JPS589685B2 - A method for filtering particles from a fluid using a filtration bed made of granular filtration media - Google Patents

Description

[Detailed description of the invention] Converted or semi-fluidized beds are known per se.

The inventors have previously patented a method of operating such a bed that involves a chemical reaction and a physical fluid-solid contact process involving the interaction between the fluid and solid particles forming the bed (
(See U.S. Pat. No. 3,374,052 to Ron and Wen, issued March 19, 1968).

In general, any bed consisting of solid particles that can be fluidized can be used as a converted or semi-fluidized bed in the process described in my above-mentioned patent no. 3,374,052.

The above prior patents by the inventors also describe equipment systems for operating conversion beds.

The device has a vertically extending column forming a cylindrical bed, the cylindrical bed being a distributor plate or other device for introducing fluid (gas or liquid) to the bottom of the bed. is supported above the means of.

The top of the bed is stopped by an upwardly movable perforated plate, which is typically a screen plate.

The amount of fluidization that occurs in the bed ranges from zero fluidization (fixed bed) to total fluidization by raising or lowering the sieve plate, in which case the fluid reaches the minimum fluidization in the bed. is introduced at a flow rate greater than the velocity.

At a constant fluidization rate that is less than the maximum fluidization rate, the sieve plate may be lowered to the point where the entire bed is substantially fixed.

By then gradually raising the sieve plate, the lowest end of the bed is fluidized first, and as the sieve plate continues to rise, the portion of the bed that is fluidized gradually increases.

At the same time, the fixed portion of the bed near the underside of the sieve plate gradually becomes smaller until the sieve plate exerts no restraining force and the entire bed becomes fluidized.

As the sieve plate rises above the fluidized bed to form a freeboard space between the sieve plate and the fluidized bed, the entire bed is fluidized, as in standard fluidized bed operation.

The only limit in this situation is the maximum fluidization rate, i.e. the speed at which the bed expands to the point where it can no longer be maintained as a bed and particles of the bed near the top surface are carried away with the fluidizing fluid. The fluid velocity must not exceed .

These parameters and methods for calculating and/or experimentally measuring them are well known in the fluidized bed operation art.

Hitherto, conversion beds have not been proposed for use in filtration processes, such as the removal of fine particles suspended in gases or liquids.

Although porous beds of granular filtration media are commonly used in filtration processes, fixed beds of progressively smaller sizes have not been recognized to have any value for such filtration processes.

This is because it was believed that as the bed size decreased, the filtration power also decreased.

However, unique advantages are obtained when the fixed part of the filter bed is used in conjunction with the fluidized part of the bed, as is possible in the case of converted or semi-fluidized beds.

During the filtration cycle, most of the filtered particles are retained within the fluidized bed section, which increases in size, but once the entire bed is fluidized, the particles are retained along with the gas or liquid released from the bed. be carried away.

As the filtered particle "cake" accumulates at the bottom of the fixed bed section, this "cake" is broken up by upward growth of the fluidized bed section, thereby disintegrating the filtered particles along with the bed's fluidized media. circulate.

Furthermore, the pressure base across the fixed bed can be maintained relatively uniform.

This new filtration method is particularly applicable in cases where filtration is difficult.

For example, the method of the invention can be used for hot gas cleaning, such as when removing particles in the range 0.5 to 50 microns from the gaseous products of coal and/or oil conversion reactors (vaporizers, combustion devices, etc.). can be used.

Insoluble ash and mineral content is obtained from the hydrogenation and dissolution of coal, which now provides a highly cost-saving treatment method in processes such as those described above.

The method can also be advantageously applied to more general applications, such as the filtration of municipal water, for example in the final treatment of filtrate from a continuous filter or from a first or second settling tank. Fixed bed filters are now used in removing bacteria and suspended BOD from overflow.

The method of the invention allows the combination of a low pressure drop across the filter bed with a relatively high liquid velocity, so that the conversion bed is more effective than in conventional fixed bed filters. It can be a targeted and efficient means of removing finely suspended solids from wastewater.

Other advantages of the method of the invention are also discussed, which represent important advantages over currently used filtration methods.

Such applications include air filtration, stack gas purification, polymer melt filtration, sewage filtration and other difficult filtration.

The invention will now be described with reference to the accompanying drawings.

Preferred apparatus for carrying out the invention are known and
The invention is described in detail in the inventor's prior patent, US Pat. No. 3,374,052.

The disclosure of this patent is incorporated herein by reference.

The apparatus shown diagrammatically in the drawings of this application is incorporated by reference in U.S. Pat.
It is similar to the device shown in No. 4052.

The device has a vertically extending cylindrical column 10 which defines a cylindrical interior space 11 (see FIG. 1).

In the lower part of the space 11 there is provided a bed 12 of granular filtration media, which bed is supported on a distributor plate 13 having a plurality of fluid supply ports 14 .

The feed ports 14 are preferably evenly distributed in all directions across the distributor plate.

The supply port 14 transfers the fluidizing gas or liquid to the filtration media bed 12.
to be introduced.

Other fluidizing material supply means may be used to introduce the fluidizing gas or liquid.

An enclosing chamber 15 is provided below the distributor plate 13.

The wall 16 of the chamber 15 may have a conical shape and thus act as a conical flow regulator.

The lower end of chamber 15 is connected to fluid supply conduit 17 .

Above the floor 12 is a sieve plate 18 that presses the upper surface of the floor.
or other stencil printing means are provided.

The sieve plate 18 is provided with a large number of holes 19, which holes are preferably distributed over the entire surface of the sieve plate 18.

Means are provided for selectively raising and lowering the sieve plate 18.

As shown, and as described in more detail in U.S. Pat. No. 3,374,052, the lower end of the vertically extending rack par 20 may be connected to the center of the plate 18 via a sleeve 21. .

Conveniently, the bar 20 and the opening in the sleeve 21 have a square or rectangular cross-section and the bar 20 is provided with teeth 22 on at least one side of its upper part.

The upper end of the column 10 is closed off by a cover plate 23, over which the rack 20 projects through a central opening in the cover plate.

A drive mechanism is coupled to the protrusion of the bar 20 and includes a pinion 24 having teeth that engage the teeth of the rack parr 20.

This pinion 24 is driven by a shaft 25 connected to an electric motor 26.

Suitable controls (not shown) may be provided for manually or automatically operating motor 26.

As shown, a drain conduit 27 extends to an opening in cover 23.

Alternatively, a drain conduit may be provided in the upper side wall of the column 10.

A series of pressure gauges 28 are provided which are connected to suitable pressure taps extending through the sidewalls of the column 10 to enable testing of pressure conditions within and across the bed 12. ing.

Although the pressure gauge shown is designed for manual operation, more complex pressure sensing and recording devices are used in automated versions of the device.

FIG. 1 shows a situation that can be used at the beginning of filtration.

The bed 12 is completely settled and the plate 18 has been lowered into intimate contact with the upper surface of the bed.

Therefore, when the fluid containing the particles to be filtered is introduced into the bed via the plate 13, the entire bed is in a stationary and non-flowing state.

In order to supply the gas or liquid to be filtered under pressure into the conduit 17 into the conical flow regulator 16 and through the supply opening 14 of the distributor plate, a suitable pump for this fluid can be used. It will be understood.

As will be appreciated, holes 19 in the sieve plate are provided to keep the filtration media between the distributor plate and the sieve plate.
Similarly, the feed openings 19 of the distributor plate also have dimensions (
cross section).

For carrying out the method of the invention, the velocity of the incoming fluid should be greater than the minimum fluidization velocity of the filtration media being used.

Generally, the fluid should have a rate of rise that is at least twice the minimum fluidization rate of the bed if it were unrestrained.

Typically, for best treatment, the rate of rise of the fluid (gas or liquid) should be at least three times the minimum fluidization rate of the bed if unrestrained.

For example, a fluidization rate in the range of about 3 to 10 times the minimum fluidization rate may be advantageous.

As the fluidization rate increases to near the maximum fluidization rate of the bed if unchecked, a portion of the bed can no longer remain non-fluidized.

This is because the particles in the bed are forced upwardly against the sieve plates, and once the maximum fluidization velocity for an unrepressed bed is reached or exceeded, the entire bed can change to a nearly stationary, non-flowing state. It is.

However, for most filtration media materials, the range between maximum and minimum fluidization rates is relatively wide, so that by lifting the sieve plate, the size of the fluidized section below the bed An appropriate rate at which the bed can be changed from a fixed state to a semi-fluidized bed while increasing gradually can be easily selected.

The method of the present invention can be more clearly understood in connection with the process sequence illustrated in Figures 1-4 of the accompanying drawings.

As shown in FIG. 1, at the beginning of filtration in the preferred process, the entire bed 12 is maintained as a fixed bed.

The fluid containing the particles to be filtered is introduced at such a rate that the entire bed would be fluidized if the sieve plate 18 were not suppressing the bed.

Furthermore, the initial position of the sieve plate 18 is such that it prevents substantial fluidization of the bed.

The bed filtration media is selected for its ability to dislodge particulate matter from the fluid, so that particulate matter cannot penetrate much into the bed before being stopped by the bed particles.

After a short period of time, a "cake" of particles begins to form at the bottom of the bed near the distributor 13, as shown in FIG.

Cake formation increases the pressure drop across the bed, which can be monitored by the distributor and the pressure catapult at the top of the bed.

When this pressure increase occurs, the motor 26 is started manually or automatically to gradually raise the sieve plate 18.

Mechanical movement of the sieve plate in conjunction with the force exerted by the fluid stream breaks up the formed cake of particles into small pieces.

The lower part of the bed also begins to fluidize, thus breaking the cake.
This is facilitated by fluidization of the particles in the cake-containing portion of the bed.

Also, due to the disintegrating action of the existing cake, many of the particles surrounded by the cake are fluidized.

FIG. 3 shows an intermediate stage of the filtration process in which the bed operates as a semi-fluidized bed, with the lower part of the bed in a fluidized state but the upper part being essentially a fixed bed.

In the semi-fluid state of operation, the particles of filtration media at the bottom of the bed are subjected to two forces.

, one force is the downward gravitational attraction, which tends to cause particles to fall from the floor under their own weight into the fluid stream.

The particles are then subjected to fluid flow forces.

The fluid stream striking the particles in the bottom layer cannot flow straight through the bed due to the packed state of the particles.

Therefore, a portion of the fluid is redirected along the bottom of the bed and exerts a force in a different direction on these particles.

The distributor mouth or hole 14 breaks up the fluid stream to form multiple jets entering the bed, so that a significant turbulence condition created by the impingement of the individual redirected flows is created along the bottom of the bed. It exists.

Such an agitated flow pulls or breaks off a portion of the bed-forming particles from the fixed bed and into the fluid stream.

As a result, the particles become fluidized.

This interaction of forces causes a small portion of the bottom of the bed to become fluidized first, while sufficient upward pressure is exerted by the fluid flow to maintain the majority of the bed in a fixed bed state.

As the sieve plate rises further, more particles are fluidized because the upward force that the fluid stream exerts directly on the fixed bed section is reduced.

That is, upward pressure continues to act and maintain the fixed bed section, but the pressure is reduced because the fluid stream encounters more fluidized particles in the direct path to the bed.

As a result, due to the weight of the particles, more and more parts of the bed become fluidized as the sieve plate moves away from the distributor, and the fixed part of the bed becomes correspondingly smaller.

The previous description assumes that the flow rate of the fluid stream remains approximately constant.

However, the degree of fluidization at any location on the sieve plate 18 can also be controlled by varying the flow rate of the fluid stream.

Generally, if the flow rate is insufficient to fluidize the particles, a fixed bed will be present even if plate 11 is not in contact with the top surface of the bed.

As the flow rate increases, two things occur simultaneously.

Since upward pressure is applied to the floor at the fixed position of the sieve plate located above the packing height,
The volume of the bed increases and the fluid stream applies sufficient force to fluidize the particles near the distributor while forming a fixed bed under the sieve plate.

As the flow rate of the fluid stream increases, more and more of the bed becomes a fixed bed, and as the flow rate continues to increase, the entire bed becomes a fixed bed, leaving no particles near the distributor.

That is, a free space is formed between the bottom surface of the bed and the distributor, and the bed is pushed upward and pressed against the sieve plate to form a fixed bed.

Although this method of operation is possible, it is not normally used in conjunction with the filtration method of the present invention.

For convenience, as noted above, the particle-containing fluid may be introduced at a substantially constant rate that is several times the minimum fluidization rate, and this rate may be maintained throughout the filtration process.

However, if further control of the process is desired, the fluid flow rate can be increased or decreased, thereby selectively varying the volume of the fixed bed section relative to the fluidized bed section.

The bed is operated as a conversion bed, which is the operating condition for most of the filtration process, during which particulate matter or cake pieces consisting of the preformed filter cake are transferred to the fluidized bed particles in the lower part of the bed. circulates with

At the same time, a cake continues to form at the bottom of the fixed bed as shown in FIG.

As the sieve plate continues to rise, the fluidized bed section expands as described above, increasing the amount of filtered particles retained in the fluidized bed section and these particles circulate along with the fluidized particles.

This process can be continued until the fixed bed portion is reduced by well over 5 to 10 times the total bed and the accumulated "cake" is present in the immediate vicinity of the sieve plate 18.

Although the filtration process may be terminated at any point, the maximum capacity of the bed may be utilized by continuing the filtration until the filtered particles are carried away through the sieve plate 18 along with the gas or liquid.

At this time, the remaining particles are present in the fluidized bed section, which has a large volume.

As the sieve plate 18 moves upward, the bed expands so that the fluidized particles in the bed become more isolated and there are spaces between the granules containing circulating filtration particles.

When the bed operates to maximum capacity during the filtration cycle,
The filtered particles fill 80 to 90 inches of the bed volume at the end of the working cycle.

The selection of a particular granular filtration media depends on the filtration process being performed.

Generally, the medium is one that can hold the granules as the gas or liquid passes through the granules while the bed is stationary.

In other words, if a granular filtration medium is suitable for gravity filtration of a particular fluid and the particles contained therein, it may be used for the purposes of the present invention.

However, according to well-known fluidization principles, it is preferred that the granules of the filtration media have relatively uniform dimensions.

For filtration purposes, the bed granules are inert to both the fluid being filtered and the filtered solids.

The packed granules act as a perforated filter.

The bed may be formed from particles or granules of sand, glass beads, or a wide variety of other granular filtration media.

The density and dimensions of the granular media are adjusted depending on the particular system to be filtered.

Particle size, shape as well as particle dimensions can be varied to adjust the filtration properties of the bed.

At the end of the filtration cycle, the introduction of the fluid to be filtered is discontinued and the sieve plate 18 is removed from the top of the column 10, such as
It is lifted to a position above the top of the floor.

A purification fluid is then introduced through conduit 17 at a rate sufficient to fluidize the entire bed 12 into a fluidized bed.

When the sieve plate 18 is lifted and the bed is completely fluidized, the cake present at the top of the bed at the end of the filtration is broken up.

As the purge fluid continues to be introduced, particles that are smaller in size and preferably less dense than the bed particles are carried away with the purge fluid.

In this way, the floor can be cleaned by almost completely removing the filtered particles.

Typically, when the bed is used to filter particles from a gas, the purification fluid is a gas, and when the bed is used to filter particles from a liquid, the purification fluid is a liquid.

However, a wide range of choices are possible with respect to the purification fluid, the only requirement being that the purification fluid carries away the particles separated by filtration while leaving behind the bed particulates.

However, if some particulate material is introduced into the freeboard space, this will be retained by the sieve plate 18.

This is because the holes in the sieve plate are smaller in diameter than the granules in the bed and are large enough for the passed particles to pass through.

The purifying fluid carrying the particles thereby filtered can be removed via outlet 27 and treated in any suitable manner.

In carrying out the filtration process, the sieve plate 18 may be raised intermittently or continuously.

If the filtration process is carried out in a relatively standard manner, the sieve plate 18 may be lifted at a slow continuous rate after the formation of the initial filter cake.

To indicate that the cake is kept at the bottom of the fixed bed,
It is important to maintain sufficient pressure drop across the bed.

If the device is operated with manual control and input observation, the operator may observe the pressure gradient by reading the pressure gauge 28 as the sieve plate rises.

In large-scale commercial processes, automatic control equipment can naturally be provided and the rate at which the sieve plate 18 is raised can be automatically controlled in relation to a preset pressure difference.

However, while these control features are preferred, they do not form part of the invention in its broadest sense.

In summary, the method provides a method for filtering fine particles from a fluid using a bed of granular filtration media configured to allow the fluid to pass through but retain fine particles contained in the fluid. do.

In practicing this method, a granular bed is supported above a fluidizing distributor in an enclosed upwardly extending zone.

The upper surface of the floor is restrained by perforated plate means mounted within the zone and adjustable to a selected height within the zone.

The pore size of the plate means is smaller than the size of the filtration media granules.

The fluid containing fine particles to be filtered is passed upwardly through a distributor and a restrained bed.

The fluid should have a rate of rise that is at least twice the minimum fluidization rate of the unrestrained bed.

A cake of particles is collected at the bottom of the bed, and the bed above the level at which this cake collects is maintained as a non-flowing fixed bed.

The plate means is gradually lifted to form an increasingly large fluidized bed below the top of the bed while fluid continues to pass through the bed.

The collected particles are retained as a cake in the fixed bed section and as a circulating solid in the fluidized bed section.

The fluid passed through the plate means is substantially free of solids.

At the end of the pass, the fluid supply is stopped and the plate means is lifted above the floor to form a freeboard space.

A purge fluid is then passed through the distributor into the bed at a rate capable of fluidizing the entire bed and removing filtration particles from the bed.

That is, the filter particles are removed along with the purifying fluid.

Preferably, the pore size of the stop plate means is larger than the size of the particles, so that the purge fluid containing particles is removed through the stop plate.

However, as an alternative to this, an outlet for the purified fluid may be provided below the distributor plate, which outlet is usually fitted with a screen or sieve plate;
The pore size of this screen or sieve plate is larger than the particles removed with the purifying fluid, but smaller than the granules of the filtration media.

In a preferred method of operation, at the beginning of filtration, the entire bed is substantially stationary, including the bottom of the bed near the distributor plate.

The first formed cake collects at the bottom of the floor.

However, if desired, the filtration process may be started with the plate means somewhat elevated, so that a small fluidized bed section can be formed directly above the distributor plate.

Even though a small portion of the bed is in a fluid state below the fixed bed, the majority of the bed is in a fixed state and an initial cake forms at the bottom of the fixed bed section.

The reason for starting filtration with the entire bed in a fixed state and continuing filtration until the cake comes near the sieve plate is to maximize the usable capacity of the bed.

However, if desired, it is also possible to carry out the whole filtration process with the bed in a semi-fluid state, in which case the proportion of the bed in a fixed state is gradually reduced.

Next, the method of the present invention will be further explained by the following examples.

Example 1 Gases generated and generated from coal and/or oil conversion reactors such as vaporizers and combustors contain particulate matter.

Small particles, ranging in size from about 0.5 to 50 microns, cannot be easily removed with conventional equipment such as cyclones, wet collectors, or electrostatic precipitators.

Because of the small size of these particulate materials, effective purification of gases containing such materials is a key to the development of advanced power circulation technologies that efficiently apply hot gases from industrial processes to gas turbines. It has become an obstacle.

The method of the present invention effectively addresses this problem.

Removal of particles from 0.5 to 50 microns can be achieved using sand or coalstone particles with a size of 300 to 1000 microns.

The surface velocity of the gas required for continuous fluidization in the method described with reference to Figures 1 to 3 is 3 to 10% of the minimum fluidization velocity.
or 1.0 to 5.0 ft/sec.

The pores in the distributor plate and sieve plate are substantially smaller in size than the pellets comprising the bed and may range from about 100 to 800 microns depending on the size of the bed material.

At the beginning of the process, the gas stream containing the particles enters the fixed bed, the particles are trapped and the cake formation process begins.

As the cake increases, it becomes apparent that the pressure drop increases, as detected by the pressure drop at the distributor and the top of the bed.

When the pressure drop increases by 5 to 15 ei/ft from the minimum value, the drive system of the upper sieve plate is activated and the sieve plate is gradually raised to form a fluidized bed at the bottom of the bed matrix and fixed at the top. Form the floor.

The rising speed of the upper sieve plate is, for example, 25 si,
Regulated by maintaining the pressure drop at a suitable value.

As the sieve plate continues to rise, the fluidized zone continues to expand, while the fixed bed zone continues to contract.

When the final stage of filtration is reached (FIG. 4), the gaseous feed stream is diverted to the second bed and the filtration process begins again.

Two or more beds may be connected to provide continuous filtration.

While one bed is being purified, the other bed is used for a filtration cycle.

A bed can be used alternately for filtration and purification by simply switching the line control valves, which switching can be done automatically.

The used bed is then cleaned to remove particulate matter that has collected in the bed during operation.

This cleaning is accomplished by simply raising the sieve plate to thoroughly fluidize the bed and blow away particulate matter.

Air is conveniently used as the purification medium, but other gases may also be used.

Example 2 Coal oil obtained by hydrogenating and melting coal contains a large amount of insoluble ash and mineral matter.

Removal of these particles is the main costly treatment in this process.

The results of the analysis of experimental data on the operation of conversion beds under heated conditions show that the process of the invention is a very successful alternative to the currently used separation methods.

The floor matrix used in this system was 0
．． 01~0. It may consist of a mixture of silica and alumina with a particle size in the range of 5 cm (density 2.7 g/cc).

The bed is heated and maintained at about 200°C to 300°C by electric heaters installed on the sides of the bed.

As will be appreciated, the fluidized bed can be heated and pressurized to conditions that adjust the fluid density and viscosity so that it can flow more easily through the bed.

For this system to operate effectively, the liquid coal oil velocity must range from a minimum of about 0.003 ft/sec to about 2 ft/sec.
It may be in the range up to seconds.

This rate should be at least 2 to 3 times lower than the minimum fluidization rate of the bed.
Should be double.

The size of the holes in the distributor plate and sieve plate may range from 0.008 to 0.3 cm.

As filtration begins and progresses, the pressure drop increases from an initial value of about 2-30 Psi/ft to about 10-45 Psi/ft, at which time the upper sieve plate drive mechanism starts and fluidizes. Induce.

The method of operation from this point on is similar to that described above.

When the upper sieve plate is raised to a height where the bed is nearly fluidized, the flow of coal oil is bypassed.

The bed is cleaned with a solvent such as benzene or toluene to remove particles by completely lifting the sieve plate and completely fluidizing the bed.

Example 3 Currently commercial municipal sewage treatment plants use sand, diatomite,
Trickle filters made of coke, charcoal, and other inexpensive fillers suitable for filtration have been used for small-scale treatment of diluted wastewater.

The best application of such a filter is found in the final treatment of lachrymal fluid from a continuous filter or overflow from a first or second settling tank.

Under normal conditions, such filters remove bacteria and suspended BO.
D can be effectively removed.

Conventional filter beds in municipal wastewater treatment plants represent fixed bed treatment.

Usually 0.3~0. In this 2 foot deep filter bed of 7 mm sized sand particles, the pressure drop across the bed ranges from 2 to 20 Psi and the flow rate through the bed is about 0.007 feet/second. be.

The pressure drop for a two foot high fluidized bed containing particles of the same size as above is about 1.2 Psi.

This fluidized bed can also handle flow rates through the bed of 0.03 to 0.2 feet per second.

This small pressure drop, combined with the relatively high liquid flow rate, makes the conversion (semi-fluidized) bed better able to remove fine suspended solids from wastewater than traditional methods. It is a more effective and efficient means of

The drive means for raising the sieve plate is activated when the pressure drop reaches approximately 5-20 Ps i and the cycle is completed as described above.

All other operating methods are similar to those described above for hot gas filtration and coal oil filtration.

Unlike the filtration method of the present invention as shown in the above examples,
If filtration is carried out in a conventional fixed bed, a cake of particles accumulates and remains at the bottom of the fixed bed with very little penetration into the bed.

Once formed, the cake removes fine particles from the F fluid.

This is because the dense cake actually acts as a filtration medium.

However, since all the pores of the cake are filled with particles, this simultaneously increases the pressure drop such that no further filtration can be carried out.

In contrast, in the present invention, as the top sieve plate gradually rises, the tightly formed cake is broken up by gravity, resulting in the formation of an increasingly large fluidized bed below the fixed bed.

The pressure drop across the filter cake is thus controlled and prevented from increasing to a level where filtration cannot continue.

Furthermore, this method of operation allows fluid to further penetrate into the fixed bed.

As the filtration progresses, the particle concentration in the fluidized bed section increases, so that the filter cake forms more rapidly in the later stages of filtration than in the early stages.

However, this is compensated for by lifting the sieve plate continuously or intermittently at increasingly faster speeds.

If the pressure drop across the filter cake and fixed bed remains relatively constant, faster formation of the filter cake is automatically inhibited.

This method of operation is therefore ideally suited for automatic control mechanisms.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a convertible bed filtration device used to remove particulates from a fluid, the bed being initially unfluidized and in a substantially fixed state; FIG. Figure 3 is a cross-sectional view of the apparatus shown in Figure 3 after a cake of filtered particles has begun to accumulate at the bottom of the fixed bed; FIG. 4 is another cross-sectional view of the apparatus showing the stages, the lower part of the bed being in a fluidized state while the upper part of the bed remains in a fixed bed state; FIG. FIG. 2 is a longitudinal cross-sectional view of the entire bed in a fluidized state to remove filtered particles after filtration is complete. 10... Cylindrical column, 12... Granular filtration medium, 1
3... Distributor plate, 14... Fluid supply port, 17... Fluid supply conduit, 18... Sieve plate, 19... Hole, 27... Fluid discharge conduit.

Claims (1)

[Scope of Claims] 1. Supporting a filter bed consisting of a granular filtering medium capable of retaining fine particles in the fluid while passing upwardly a fluid containing fine particles to be filtered; from the fluid in a limited zone extending upwardly from the fluid intake means, comprising perforated plate means movable upwardly to arrest the upper surface and having holes of a size smaller than the particles of said passing medium. A method for filtration of fine particles, comprising: (a) through a fluid intake means and a top-blocked furnace filter bed at least 2 times the minimum fluidization rate for a filter bed with an unblocked top; (b) passing the fluid upwardly at twice the speed; (b) filtering the filter bed between the plate means and the zone bottom while restraining the upper surface of said bed with plate means to make the bed a non-fluidized fixed bed; C) collecting fine particles to form a cake at the bottom of the fixed bed section of the filter bed; (d) by lifting the plate continuously or intermittently while continuing to pump fluid into the filter bed; , crush the lower part of the cake to form a fluidized bed part below the fixed bed part, and then gradually increase the proportion of the fluidized bed part in the furnace bed, while as the proportion of the fixed bed part decreases. The cake re-formed from the fine particles collected in the fixed bed section is re-pulverized and retained as a solid that circulates in the enlarged fluidized bed section; (e) After stopping the fluid feed, the plate is placed in the furnace bed. (f) flowing a purifying fluid into the bed at a rate sufficient to fluidize the entire filter bed and sweep fine particles from the bed; , the fine particles are removed together with the purification fluid. 2. The method according to claim 1, characterized in that the initial stage of the filtration is a furnace.